SmartCheck
Keeping proof for many years
What it takes for it to still hold in ten years.
A seal does not expire with time, but the cryptography behind it ages: what is impossible to forge today may not be in twenty years. For documents that have to last, that needs anticipating.
What is needed and when
| Document's lifespan | What it needs |
|---|---|
| Under 5 years | Nothing special. Keep the file |
| 5 to 15 years | Keep the original file, unconverted |
| Over 15 years | Plus re-sealing before the algorithm becomes obsolete |
What usually fails is not the cryptography
It is losing the file. Documents that stop being provable after ten years rarely fail on the algorithm: they fail because nobody knows where the file is, or because someone converted it to another format "to archive it better" and thereby changed its fingerprint.
Important
Converting a sealed file to another format invalidates it as evidence. Keep the original exactly as it was sealed, and if you need a copy in another format, make it an additional copy, not a replacement.
What to keep, exactly
- The original file, byte for byte.
- The sealing receipt.
- And knowing where both are in ten years, which is the hard part.
Worth knowing
If the document lives on the platform, your retention policy covers this. The problem appears with copies people take to their own drives and later reorganise.
›Am I warned when re-sealing is due?
Ask about it for your long-lived documents: it is not something to discover late.
›Does re-sealing change the document?
No. It adds a new layer over the same fingerprint.
›What if I lose the receipt?
If the document is on the platform, it is recovered. If you only had a loose copy, that is the problem.
A real case
The situation
An engineering practice keeps projects that may be disputed twenty years later.
What you do
- Keeps the originals unconverted
- Asks about re-sealing for the longest-lived ones
What you get
The projects remain provable when a claim appears fifteen years on.
The situation
The proof is stored in a format nothing will open in ten years.
What you do
- Keeps the original in a standard format
What you get
The file stays readable.
The situation
The evidence lives on a machine that gets retired.
What you do
- Stores it off personal machines
What you get
Migration does not take the proof with it.
The situation
The document is kept and the seal reference is lost.
What you do
- Keeps document and reference together
What you get
Verification stays possible.
The situation
Systems change and the history is left behind.
What you do
- Includes the proof in the migration plan
What you get
The evidence survives the change.
The situation
Nobody ever checks whether the proof still verifies.
What you do
- Verifies a sample periodically
What you get
A problem is found before the proof is needed.
This article answers
- how long does a seal remain valid
- long-term preservation of signed documents
- re-sealing old documents
- will it still hold in ten years